Research progress and prospects on the hydrodynamic characteristics of two-phase flow in reactor coolant pumps under non-uniform inflow

In the design of the third-generation nuclear power plant, two vertical reactor coolant pumps (RCP) are installed upside down at the bottom of the steam generator, which is limited by the space of the first circuit, and the channel-head of the RCP-steam generator adopts a short straight pipe design, which causes the inlet of the RCP to be non-uniform flow. The design of the RCP generally assumes uniform inlet flow conditions, but it actually operates under non-uniform conditions. The RCP is a key equipment that affects the safety and economy of nuclear power plants. When accidents such as water loss, stuck shaft, or power failure occur, it can lead to extreme working conditions in the gas-liquid two-phase four-quadrant such as reversal, counter-flow, braking and shutdown. Understanding the hydrodynamic characteristics of the RCP's gas-liquid two-phase flow is crucial. Currently, pump gas-liquid two-phase flow research primarily focuses on uniform straight pipe flow, with the impact of non-uniform flow not yet considered. Therefore, this paper will carry out the research progress and prospect of the hydrodynamic characteristics of two-phase flow under the RCP with non-uniform flow. Firstly, the necessity and importance of research are introduced from the perspectives of the first-circuit system of the RCP and the gas-liquid two-phase flow. Secondly, focusing on the non-uniform flow of the RCP and other pumps, the research overview of the influence of non-uniform flow on the hydrodynamic performance of the pump is introduced. Thirdly, based on the gas-liquid two-phase flow of various pumps, the numerical calculation and experiment methods of gas-liquid two-phase flow in the pump are introduced, the distribution and hydrodynamic characteristics of the two-phase flow in the pump under different gas content rates are introduced. Finally, the research direction and future development trend of gas-liquid two-phase flow in the pump are prospected.